Various devices for coupling a chronograph mechanism are known to those skilled in the art. EP Patent Application 2897003 discloses a conventional coupling device for a chronograph mechanism. This coupling device includes an intermediate wheel which, when the coupling is engaged (device in the coupled state), simultaneously meshes with a chronograph wheel and a drive wheel and which, when the coupling is disengaged (device in the uncoupled state), is removed from at least one of these two wheels to break the kinematic chain between them. To this end, the coupling device includes a coupling lever which carries the intermediate wheel at the end of one of its two arms and which is associated with a first return spring so that the end of the second arm of the coupling lever remains resting against a column wheel. The column wheel thus forms a kind of cam and the aforementioned end of the coupling lever forms a cam follower. To actuate the column wheel which alternately controls the coupling and uncoupling of the chronograph mechanism, there is provided a large lever which at one carries end a pivoted click associated with a second return spring.
The conventional coupling mechanism described above is complex. It comprises several pivoted members including a column wheel, which is a complex and therefore relatively expensive component. The two aforementioned springs generate friction forces in the mechanical contact areas provided, which results in wear. Moreover, such springs are fragile and their elasticity may vary with age. Finally, the various members must be precisely assembled in the timepiece in order to be functional, particularly the click actuating the column wheel and the large lever which generates the back-and-forth motion of the click.